From what I recall, the VIA line of GPUs isn't exactly Linux-friendly, to say the least. Now, VIA claim the VX855 supports Linux - but they claim that about a lot of their hardware that doesn't have any sort of usable Linux graphics drivers.

Also, the original OLPC had a custom firmware with all sorts of neat features designed for easy deployment and upgrading. Are they dropping that?

Plus, the release announcement says the new hardware doesn't support mesh networking, at least not yet.